test_data_download_worker: use aom-test-data bucket
test_data_download_worker: use aom-test-data bucket

this will help segregate av1 test vectors and regression files from
those in libvpx

Change-Id: I2bd034016f21374e6924800b730a67f9c3017e3a

GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom